In the related art, there has been known an intake device including a rotary shaft and an intake valve that is rotated within an intake port together with the rotation of the rotary shaft to change intake air (see, e.g., JP 2010-001847A (Reference 1)).
Reference 1 discloses an intake device that includes a resin-made intake control valve (intake valve) that is disposed in each of four intake pipe portions (intake ports) to be rotated between an opened position and a closed position, a common shaft (rotary shaft) that rotates respective intake control valves in unison, and an actuator that rotates the shaft. Each intake control valve in the intake device described in Reference 1 has a shaft penetrating portion into which the shaft is inserted. Through holes (rotary shaft press-fit holes) each having a rectangular shape in cross section are respectively formed at the opposite end portions in the rotary axis direction of the shaft penetrating portion. In addition, the opposite end portions of the shaft penetrating portion are configured as sliding portions (rotary shaft portions) rotatable with respect to bearing parts arranged on the intake port side, and the through holes are formed inside the sliding portions (rotary shaft portions). In addition, since the shaft having a square shape (rectangular shape) in cross section is press-fitted into a pair of through holes (rotary shaft press-fit holes) provided at the opposite end portions of the shaft penetrating portion, the intake control valves are fixed to the shaft.
However, in the intake device of Reference 1, since the press-fitted positions (fixed positions) of the shaft are disposed at the opposite end portions of the shaft penetrating portion, the press-fitted shaft (rotary shaft) itself is likely to be bent and deformed due to the warpage of the resin-made intake control valves (intake valves) along the rotary axis direction. As a result, there is a problem in that the opposite end portions of the intake control valves are likely to be axially displaced from each other, so that the rotating resistance of the sliding portions (rotary shaft portions) with respect to the bearing parts increases. In addition, when uneven wear of the bearing parts occurs due to the axial displacement of the sliding portions (rotary shaft portions), leakage of intake air is likely to occur between the intake pipe portions (intake ports) which are adjacent to each other through a gap formed between the sliding portions and the bearing parts. For this reason, intake air pulsation (intake inertia effect) cannot be effectively obtained due to the degradation of the sealing property of the intake control valve (intake valve), and there is a problem that the engine performance is degraded.
Thus, a need exists for an intake device which is not susceptible to the drawback mentioned above.